For next-generation mobile communication, there is a need to provide high-speed high-quality data transmission to support a variety of multimedia services with higher quality. Recently, intensive studies have been carried out on Orthogonal Frequency Division Multiplexing Access (OFDMA) and Single Carrier Frequency Division Multiple Access (SC-FDMA) as methods to meet such a need.
The Orthogonal Frequency Division Multiplexing (OFDM) method that is a basis of the OFDMA method has been widely considered as a physical layer transport method for a variety of wireless communication systems such as wireless LANs, digital TVs, and next-generation mobile communication systems since the OFDM method has an advantage in that it enables high-speed communication with low equalization complexity in frequency selective fading channels.
Control channels in a communication system are common channels through which transmitting and receiving sides can exchange the same information with each other. The control channels are configured to suit a basic protocol structure in which the system operates.
Although the present invention is not limited to the IEEE 801.16 system, the following description will be given with reference to the IEEE 801.16 frame structure as an example for ease of explanation.
FIG. 1 illustrates a Time Division Duplex (TDD) frame structure of the IEEE 801.16 communication system.
Every transmission frame has a specific length and may include a preamble indicating the start of the frame, a MAP containing information of use of the frame, located subsequent to the preamble, a Frame Control Header (FCH) indicating configuration information of the MAP, a data burst section which can be used for general purposes, an uplink data section, and an uplink-related control channel. Here, the data burst section may include a variety of zones and the uplink data section may also include zones.
A radio frame illustrated in FIG. 1 includes a downlink subframe and an uplink subframe. The downlink frame starts with a preamble for synchronization and downlink transmission and includes a control information field and a data field. The control information field includes control information such as an uplink MAP (UL-MAP) message and a Downlink MAP (DL-MAP) message for providing resource allocation information of each user terminal (or mobile station).
The DL-MAP message of the downlink frame includes DL-MAP IEs of each user terminal and shared information such as a base station ID, a Downlink Channel Descriptor (DCD) count, a physical layer (PHY) synchronization field, and a management message type. Each DL-MAP IE includes OFDMA symbols and subchannels for each PHY burst of a data area and associated Downlink Interval Usage Codes (DIUCs) and defines downlink transmission using these components.
The UL-MAP message included in the uplink frame includes UL-MAP IEs of each user terminal and shared information such as an allocation start time, an uplink Channel Descriptor (UCD) count, an uplink channel ID, and a management message type. Each UL-MAP IE includes a Connection Identifier (CID) and associated Uplink Interval Usage Codes (UIUCs) and defines uplink transmission using these components.
Accordingly, each terminal which operate in the system searches for such control channels and receives various cell information that enables use of this or subsequent frame. The channel or frame structure should not be changed to successfully perform these processes.
However, when the actual system evolves as in IEEE 802.16m, the system has new features and the legacy control channel structure needs to be changed to reflect the new features. Therefore, there is a need to generate a compatible channel structure. For this need, it is not possible to completely overcome problems of the legacy system.
To meet various system requirements, legacy structures are maintained for compatibility even when a time varying system is enhanced due to the cell size, the terminal travel speed, or the like and thus new terminals of the enhanced system have the same problems as those of the legacy system.
That is, a method of improving performance and efficiency of use of legacy channels is generally used to enhance the legacy system. However, the enhanced system is implemented with the same problems as those of the legacy system.